It is well known that compositions, containing hardenable, unsaturated polyesters, epoxy acrylates, urethane-forming isocyanates and/or epoxides can be used for fastening anchor rods in boreholes without expansion pressure. For this purpose, the compositions, together, with the hardener, are introduced into the borehole. To accomplish this, the compositions, mixed and measured out, can also be applied in a borehole by means of cartridges, squeeze-out devices and static mixers. It is also possible to fabricate the hardenable component and the hardener, that is, the respective starting components, in two compartments of a cartridge. By introducing the anchor with rotation into the borehole containing the cartridge, the compartments are destroyed and the two components are mixed.
The strength level of the fastening finally attained depends, above all, on the adhesive system and the degree of filling.
Unsaturated polyester resin systems, based on o- and/or isophthalic acid, maleic acid or fumaric acid as dicarboxylic acid and dialcohols have certain weaknesses with respect to the more stringent requirements for fastenings. The previous limits of the systems are the deformability when subjected to the action of heat, the ageing--especially when acted upon by moisture, temperature changes and alkalinity--strong shrinkage, deficient adhesion and inhibition of surface curing by oxygen. The epoxy acrylates, condensates of methacrylic acid and/or acrylic acid with epoxide compounds based on bisphenol A, bisphenol F or novolaks, have a greater resistance to the effects of the climate and especially to those of alkalinity, and improved adhesion properties with respect to unsaturated polyester resins. However, the three dimensional cross linking of the epoxy acrylates is less. Shrinkage and inhibition of surface curing due to oxygen are comparable with those of unsaturated polyester resins. Polyurethanes have very good adhesion properties, but, if their pot life is adequate, then their curing time is significantly longer than that of polyester resins and epoxy acrylates, which are cured with the help of free radical initiators. They react sensitively with side reactions in the presence of moisture because of the competing reaction with water, as a result of which disorders in the structure (foam structure) result, which weaken the bond. Finally, epoxide resins also have a very long curing time and cannot be used at temperatures below +5.degree. C. Their curing systems for low temperatures are moisture-sensitive. Their adhesion properties at room temperature are very good.